1. Field of the Invention
The present invention relates to a method for manufacturing an LCD device substrate, and, more particularly, to a method for manufacturing a thin film diode substrate of a liquid crystal display device having thin film diode arrays.
2. Description of Related Art
Currently, the active matrix liquid crystal display (LCD) devices are the main products of the flat panel display devices. In the known method for manufacturing a thin film transistor (TFT) liquid crystal display device, the method including five photomasks (or photolithographical steps) is frequently used. Actually, most of the current TFT liquid crystal display devices are produced by methods including four to six photomasks. On the other hand, even though manufacturing methods comprising less than four photomasks are suggested, those methods are not used or approved in the mass-production of TFT liquid crystal display devices. Furthermore, there is another option for the bottom substrate of an active matrix LCD, i.e. the thin film diode (TFD) bottom substrate. The TFD bottom substrate for the active matrix LCD has market potential since the process of manufacturing the LCD devices is relatively simple. Moreover, the cost for the apparatus for manufacturing a TFD-LCD device is relatively low.
Many problems for the manufacturing-process generate as the size of the manufactured LCD device increases. For example, the yield of manufacturing is low for large-sized panels. For the manufacturing process of the TFD-LCD devices, the decreasing of the number of the photomask means effective saving for the time, and indicates significant reducing of the cost.
Taking the process for manufacturing the bottom substrate of the TFD-LCD device for example, the common number of the used photomask is three, especially for the bottom substrate with silicon nitride (SiNx) insulation. In most cases, the first photomask is used to pattern the conductive metal layer and the bottom metal of the thin film diode. The second photomask is used to form the patterned insulation layer of the diode. The third photomask is used to form the display area and the upper metal of the diode. The product can be seen in FIG. 1. As shown in FIG. 1, signal lines S1, S2, thin film diodes 100, and display areas 200 are formed through the method illustrated above. On the other hand, a method for forming thin film diodes through anode oxidation is disclosed in the prior art JP080-32045. The thin film diode is formed by depositing a Ta2O5 insulation on the tantalum layer in the prior art. Through the steps illustrated above, only two photomasks are required for manufacturing.
Even though the number of the photomask is not high, however, a process with lower number of photomask is still needed for simplifying the manufacturing process, and reducing the cost for manufacturing.
Therefore, it is desirable to provide an improved method to mitigate the afore-mentioned problems.